Beef is typically obtained from cattle (beef cattle or dairy cattle) that have grazed in pastures and have fed in feedlots. About 18 to 24 months after birth, the animals are slaughtered and primal cuts are obtained.
The bacterium E. coli is a natural inhabitant of the gastrointestinal (GI) tract of most warm-blooded animals, including man and cattle. Over 200 serotypes or strains of E. coli have been identified, and most are non-pathogenic. In 1971, however, E. coli was first recognized as a cause of food borne illness in the United States when contaminated imported cheese caused diarrheal disease in about 400 individuals. Evidence that certain strains of E. coli were associated with human disease grew, and now five classes of "enterovirulent" E. coli are recognized as food borne pathogens causing diseases ranging from traveler's diarrhea to the potentially deadly hemorrhagic colitis/hemolytic uremic syndrome. Red meat (including beef) and poultry have been implicated as prominent sources of enterovirulent E. coli. One strain of enterovirulent E. coli is 0157:H7. Presence of this specific strain is considered as an adulterant by the USDA.
At slaughter of cattle, the carcases are inspected and graded and tested for Eschericia coli O157:H7 (E. coliO157:H7) content on a random basis. Ground beef is also randomly tested specifically for E. coliO157:H7. Meat found with E. coli O157:H7 is not suitable for human consumption and is destroyed. Meat found negative for E. coliO157:H7 and with an acceptable level of E. coli content or which were not tested for E. coli content is usually vacuum packaged to preserve freshness, and the packaged meat is sent to supermarkets or other meat distribution businesses where the vacuum packaging is removed and the meat is repackaged or displayed in a case for sale, or cuts are converted into ground meat or cut into smaller cuts which are repackaged or displayed in a case for sale.
We turn now to approaches for reducing the pathogen content of beef One approach in the battle against food borne pathogens is to reduce the occurrence of these pathogens at the farm Many food borne pathogens (including E. coliO157:H7) are inhabitants of the GI tract and feces of cattle. During slaughter and processing, fecal contaminants from the hide, hair and hooves can be transferred to the carcass, and in current processing schemes there is no foolproof means of eliminating these pathogens from raw meat products. Since the origin of these pathogens tends to be the GI tract, it is thought that by manipulating animal feed, the environment of the gut can be altered to enhance the growth of healthy non-pathogenic bacteria in the gut, and/or minimize or eliminate the presence of pathogens; this approach has not been entirely successful.